IN IN270DE2012A
A method and an apparatus for detecting an earth fault on a three-phase electric line, the apparatus comprising means (40) for determining a neutral admittance on the basis of a residual current and a residual voltage, means (40) for comparing the determined neutral admittance to a predetermined operation characteristic to detect an earth fault on the three-phase electric line (30), and means (40) for determining one or more harmonic components of the residual current and one or more harmonic components of the residual voltage, which harmonic components have frequencies n*fn such that n≥2 and fn is a fundamental frequency, wherein the means for determining a neutral admittance are adapted to use at least one of the determined one or more harmonic components of the residual current and at least one of the determined one or more harmonic components of the residual voltage for the determining of the neutral admittance. (Figure 1)
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